APEX can be interfaced directly with SWAT using either the ArcAPEX interfaces (Tuppad et al., 2009) or the SWAPP interface (Saleh and Gallego, 2007). Citation information for both of those papers are included in the SWAT literature database.

Abstract:

The Agricultural Policy/Environmental eXtender (APEX) model was developed by the Blackland Research and
Extension Center in Temple, Texas. APEX is a flexible and dynamic tool that is capable of simulating a wide array of
management practices, cropping systems, and other land uses across a broad range of agricultural landscapes, including
whole farms and small watersheds. The model can be configured for novel land management strategies, such as filter strip
impacts on pollutant losses from upslope crop fields, intensive rotational grazing scenarios depicting movement of cows
between paddocks, vegetated grassed waterways in combination with filter strip impacts, and land application of manure
removed from livestock feedlots or waste storage ponds. A description of the APEX model is provided, including an overview of all the major components in the model. Applications of the model are then reviewed, starting with livestock manure and other management scenarios performed for the National Pilot Project for Livestock and the Environment (NPP), and then continuing with feedlot, pesticide, forestry, buffer strip, conservation practice, and other management or land use scenarios performed at the plot, field, watershed, or regional scale. The application descriptions include a summary of calibration and/or validation results obtained for the different NPP assessments as well as for other APEX simulation studies. Available APEX GIS‐based or Windows‐based interfaces are also described, as are forthcoming improvements and additional research needs for the model.